Function verify 

pub fn verify(query: &str, chunk_content: &str) -> VerificationVerdict

Verify one retrieved chunk against the query that retrieved it.

Returns VerificationVerdict::Corroborated whenever either side has no extractable content terms (an all-stopword query, or empty chunk content) — verification abstains rather than penalizing degenerate input, since a false “uncorroborated” would silently drop a possibly-relevant result for a reason unrelated to actual relevance.